June 25, 2010

Researchers Call for 'No-Regrets' Approach to Climate Warming

TUCSON, AZ (UNIVERSITY OF ARIZONA)
- Two prominent climate experts, including one from the University of
Arizona, are calling for a "no-regrets" strategy for planning for a
hotter and drier western North America.

Their advice: use water
conservatively and continue developing ways to harness energy from the
sun, wind and Earth.

Jonathan Overpeck, principal investigator
with the Climate Assessment for the Southwest at the UA, and Bradley
Udall, director of the Western Water Assessment at the University of
Colorado, write in the June 25 issue of the journal Science that such
an approach is necessary for coping with a wide range of projected
future climate changes in the West and Southwest.

In their
overview of shifting climate in the region, Overpeck and Udall cite
published findings of prevalent signs of change: rising temperatures,
earlier snowmelt, northward-shifting winter storms, increasing
precipitation intensity and flooding, record-setting drought,
plummeting Colorado River reservoir storage, widespread vegetation
mortality and more large wildfires.

"The West, and especially the
Southwest, is leading the nation in climate change – warming, drying,
less late-winter snowpack and drought – as well as the impacts of this
change," said Overpeck, a UA professor of geosciences and atmospheric
sciences and co-director of the Institute
of the Environment.

In the past 10 years, temperatures
in almost all areas in western North America have surpassed the 20th
century average, many by more than 1 or even 2 degrees Fahrenheit.

The warming has decreased late-season snowpack, which serves as a
water reservoir, as well as the annual flow of the Colorado River, the
researchers said.

Those reductions, combined with the worst
drought observed since 1900, haven't helped matters; water storage in
Lakes Powell and Mead, the largest southwestern water reservoirs, fell
nearly 50 percent between 1999 and 2004 and has not risen significantly
since.

In addition to water, vegetation is feeling the effects
of climate change. Work by UA's David Breshears and colleagues have
already showed that more than 1 million hectares of piñon pine have
died in the Southwest in the last few decades from a lethal combination
of record-high temperatures and uncommonly severe drought.

In
addition, the frequency of large wildfires has increased as snowpack
has decreased.

While researchers are confident that the higher
temperatures and resulting changes in snowpack, Colorado River flow,
vegetation mortality and wildfires are human-caused, they don't know
whether the drought that has plagued the West for the last 10 years –
the worst since record-keeping began – is because of humans, Overpeck
said.

"It's critical to determine the causes of the observed
change, including the drought, because then we will have a much
improved ability to say what's coming next, in the future," Overpeck
said.

To complicate issues, studies published to date suggest
that Colorado River flow could continue to decrease by 20 percent by
2050, with severe implications for cities served by Colorado River
water and for agricultural production.

"One thing is for sure,"
Overpeck said. "The best strategy now – the no-regrets strategy – is to
prepare for a hotter and drier West, Southwest and Arizona, and to
make sure we don't commit water to things now in ways that could make
water shortages in the future more difficult to deal with."

Fortunately,
Overpeck said, scientists have a better understanding about potential
future climate change in western North America than for many other
regions around the globe, making it easier for policy makers to plan
coping strategies.

The researchers also point to the region's
potential wealth of solar, wind and geothermal renewable energy
production.

"That offers a way to make up economically for the
costs that will be incurred in adapting to the warmer, drier
conditions," Overpeck said. "And it will have the side benefit of
decreasing the chances, through reducing greenhouse gas emissions, for
potentially greater human-caused climate change."